Machines that continuously and automatically produce large quantities of flake ice are well known for use by the food processing industry, onboard seafood processing ships, within grocery food stores, and for cooling concrete in construction. Flake ice machines have been developed that utilize a rotating cooling disk that is cooled by flow of a refrigerant through internal passages formed in the disk. Water or other liquid to be frozen is introduced to a portion of the side surfaces of the rotating disk, is sub-cooled, and is then removed as the disk rotates between a pair of ice removal blades positioned adjacent the side surfaces of the disk. An example of such a conventional flake ice machine is disclosed in U.S. Pat. No. 5,307,646 to Niblock, the disclosure of which is hereby expressly incorporated by reference.
In such conventional disk ice machines, the cooling disk is mounted on a hub for rotation about the central axis of the disk. As with all manufactured pans, disks tend to exhibit some axial runout, which causes the circumferential edge of the disk to wobble during rotation. The ice removal tools on each side of the disk must be spaced apart from the side surfaces of the disk to accommodate the disk wobble and to avoid the blades contacting the disk surfaces. Such contact would result in rapid wear of the disk surfaces. The wobble effect is most pronounced at the circumferential edge of the disk, and thus this determines the spacing of the blades relative to the disk. In conventional flake ice machines, a clearance of approximately 0.010 to 0.012 inches is maintained between each rigidly mounted blade and the corresponding disk surface to prevent premature wear of the disks, which are costly to produce.
However, the spacing required between the disk and the ice removal blades of conventional machines places the blades further from the shear joint defined between the frozen ice and the underlying disk surface. This makes removal of the ice more difficult. In some instances, the blades incompletely remove ice from the cooling surfaces, and a tough layer or bumps of ice will stubbornly remain on the disk after passing through the blades. This effect is especially pronounced nearer the peripheral edge of the disk, because of the high structural strength of the ice formed at the annular outer corners of the disk. Further, because of the inherent flexibility of the metal materials from which cooling disks are formed, the radially outer edge of the disk is readily deflected during rotation by the blades pushing against strongly adhered ice. Problems of incomplete ice removal and disk wobble are most pronounced near the radially extreme portions of conventional disks.
Typically, conventional flake ice machines used to produce ice must be supplied with water having a small quantity of salt that is added to increase ductility of the ice, and to facilitate complete removal of ice from the cooling surfaces in large flakes. A salinity of 150-1,000 ppms, and most typically 250-500 ppms, is conventionally utilized to facilitate ice removal. Conventional disks may be outfitted with resiliently mounted blades or flexible blades for use in making salt-containing ice. The use of flexible or resiliently mounted blades is intended to eliminate or to permit reduction in the clearance between the blades and the disk. However, the use of salt is often undesirable for ice used for some purposes, including ice being used to cool food in grocery stores. Because fresh water ice is more difficult to remove, and particularly to remove in desirably large flakes rather than smaller pieces, a rigidly mounted blade must be utilized to develop the required shear force. As noted previously, the use of rigid blades requires the maintenance of a large clearance between the blades and the disks. As a result, many conventional flake ice machines are not suitable for the production of fresh water ice.
Another conventional flake ice machine disclosed in U.S. Pat. No. 5,157,939 to Lyon et al. attempts to deal with the problem of axial runout of the disk by utilizing a harvesting blade assembly that carries a bearing block to position the disk. The bearing block contacts either side of the disk at a location radially offset from the ice harvesting blades. However, this design is not very effective, because it merely causes the harvesting blade assembly to move axially, following the disk, in response to runout of the disk. Further ice tends to build up between the flat bearing block surfaces and the flat disk surfaces, thus still resulting in undesirable deflection of the disk relative to the ice harvesting blades.